PXMOD Implementation

Acquisition and Data Requirements

Image Data	A dynamic PET data set.
Blood Data	Blood activity sampled at a peripheral artery from the time of injection until the end of the acquisition.
Tissue TAC	A regional time-activity curve from a representative brain region. It is presented as a Logan plot and can be used to define the linear segment where regression analysis should be done.

Blood Preprocessing

Decay correction is the only blood correction option.

PXMOD Logan Blood Pre-Processing

Model Preprocessing

The Logan graphical plot is performed with the TAC from a tissue VOI (TAC1) and presented to the user. In this plot, the TAC should become linear after an equilibration time. The slope of the linear segment equals the total distribution volume. The user must decide on the beginning of the linear segment and specify this time (which is NOT in acquisition time) in the model configuration. An alternative is to apply an automatic criterion for determining this start time.

PXMOD Logan Model Pre-Processing

t*	The linear regression estimation should be restricted to a range after an equilibration time. t* marks the beginning of the range used in the multi-linear regression analysis. It can be fitted based on the Max. Err. criterion. Note that the t* is in acquisition time.
Max Err.	Maximum relative error ( (measured-predicted)/predicted ) allowed between the linear regression and the Logan-transformed measurements in the segment starting from t*.
Threshold	Discrimination threshold for background masking.
Vt	Distribution volume = slope of the linear regression to the Logan plot.
Intersect	Intercept of the linear regression line.
Start	Start time of the first frame in the linear section .

The Logan plot is shown in the preprocessing Result. The user should consult this plot in order to check whether the Start time is adequate.

PXMOD Logan Model Pre-Processing Result

Map Parameters

PXMOD Vt Methods Model Parameters

The regressions in pixel-wise processing (all 3 methods) only use the data segment determined by Start Lin in the Model Pre-Processing area.

Vt_logan	Total distribution volume calculated with standard Logan plot.
Vt_perpend	Total distribution volume calculated with the Logan plot using perpendicular distances.
Vt_ma1	Total distribution calculated using Ichise's MA1 method. This method has less bias, but more variance and the maps often are contaminated by outliers.
A1	First regression coefficient of the MA1 method. Provides a sort of "perfusion" image which may be helpful for the anatomical correlation or matching.
Intercept	y-Intercept of standard regression line.
-A2	Second regression coefficient of the MA1 method.